Chemically modified polysaccharides

Adhesive Glazes, icings, frostings, wall paper paste 

Crystallisation inhibitor Ice cream, sugar syrups, frozen foods 

Coating agent Confectionery, fabricated onion rings 

Eilm former Sausage casings, protective coatings, paper sizing 

Suspending agent Chocolate milk, drilling fluids 

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Matsumoto T, Numata M, Anada T et al (2004) Chemically modified polysaccharide schizophyllan for antisense oligonucleotides delivery to enhance the cellular uptake efficiency. Biochem Biophys Acta 1670 91-104... 

Kost, J., and Shefer, S., 1990, Chemically modified polysaccharides for enzymatically controlled oral drug delivery. Biomaterials 11 695-698. 

Schmidt (2003) Chemically modified polysaccharides. GB2386900 (applicant Johnson Johnson Medical Ltd.)... 

As noted in this section, there are commercial sources of a number of polysaccharides from a wide variety of sources. Further, the technology exists to permit the commercial usage of chemically modified polysaccharides which can replace currently used polymeric materials. 

Donnelly 13) describes the use of galactose oxidase in combination with catalase for the oxidation of guar gum to produce products with various viscosities or gels under mild conditions for food applications. Oxidized guar gum and locust bean gum can also be used as precursors for various chemically modified polysaccharides. Yalpani and Hall exploited the aldehyde functionality to attach various functional groups via reductive amination, oxidation, and reduction 14), Oxidized guar can also be further oxidized chemically to obtain a... 

Pectin is used in foods in two forms, high methoxyl pectin and low methoxyl pectin. High methoxyl pectin is the form normally found in fruit while low methoxyl pectin is a chemically modified pectin. Pectins are acidic polysaccharides that occur in the cell walls of fruit. The commercial source of pectin is either citrus peel or apple pomace. The citrus peel is the residue from the production of citrus juices while apple pomace is the residue of cider production. Thus pectin is a by-product of either cider or fruit juice production. 

Based on the theory, the separation of enantiomers requires a chiral additive to the CE separation buffer, while diastereomers can also be separated without the chiral selector. The majority of chiral CE separations are based on simple or chemically modified cyclodextrins. However, also other additives such as chiral crown ethers, linear oligo- and polysaccharides, macrocyclic antibiotics, chiral calixarenes, chiral ion-pairing agents, and chiral surfactants can be used. Eew non-chiral separation examples for the separation of diastereomers can be found. 

The present chapter deals with molecular characteristics of synthetic polymers. Numerous natural polymers such as the most polysaccharides can be tentatively incorporated into this group of macromolecular substances because their behavior in many aspects resembles that of the synthetic polymers and also because they are often chemically modified to adjust their utility properties. The typical example is cellulose, the most abundant organic polymer on earth. 

Regioselective enzymatic acylation of large, insoluble polysaccharides is still a quite difficult task and therefore it is not surprising that only scant data have been reported up to now, most of them describing reaction outcomes which met with limited success. Nevertheless, enzymatic derivatization of polysaccharides has been performed in nonpolar organic solvents using insoluble polysaccharides with soluble [51] or suspended enzymes [52]. Chemically modified celluloses with either enhanced solubility or more readily accessible hydroxyl groups, like cellulose acetate or hydroxypropyl cellulose, were acylated by CalB, as reported by Sereti and coworkers [53]. However, the same authors failed to modify crystalline cellulose under the same reaction conditions. 

The chemical-enzymic approach to the synthesis of modified polysaccharides presents a good prospect for the preparation of small quantities of these polymers, which may prove very useful for immunochemical studies. The approach is certainly not limited by the specific case of Salmonella polysaccharides 10-12, and may well be extended to other polymers. The first results from this group322 show that several analogs of O-specific polysaccharides (18) of Salmonella serogroups C2 and C3 may be prepared through this approach. 

Starch is an abundant, inexpensive polysaccharide that is readily available from staple crops such as com or maize and is thus is mostly important as food. Industrially, starch is also widely used in papermaking, the production of adhesives or as additives in plastics. For a number of these applications, it is desirable to chemically modify the starch to increase its hydrophobicity. Starch modification can thus prevent retrodegradation improve gel texture, clarity and sheen improve film formation and stabilize emulsions [108], This may, for example, be achieved by partial acetylation, alkyl siliconation or esterification however, these methods typically require environmentally unfriendly stoichiometric reagents and produce waste. Catalytic modification, such as the palladium-catalyzed telomerization (Scheme 18), of starch may provide a green atom-efficient way for creating chemically modified starches. The physicochemical properties of thus modified starches are discussed by Bouquillon et al. [22]. 

Carbohydrates, in the form of gums, polysaccharides, oligomers, and monomeric sugars, are readily available in large quanitities from renewable biomass resources. Each of these substances, either directly or in a chemically modified form, is a source of intermediates (derivatives) that have potential use in adhesive formulation. Carbohydrates have been utilized historically for and in adhesives and are likely to be used more and more in the future as petroleum-derived chemicals become scarce and prices increase. Appropriate research emphasis can effectively further their use as adhesive raw material. 

Finally, nature also takes polysaccharides and chemically modifies them to make use-fill structures. Chitin is a classic example and can be thought of as cellulose with one hydroxyl group on each monomer replaced by an acetylamino group, as illustrated in Figure 9-38. This allows for increased hydrogen ... 

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